One or two conventional projectors are conventionally used in the case of simultaneous projection of two images or two films onto a projection surface. The projector or projectors may then display the two images or films adjacent to one another, for example, recognizable for all observers simultaneously.
Projecting two partial images of a 3D image onto the projection surface so that the partial images are superimposed, and only one of the two images is recognizable for each eye of an observer, is known from stereogram projection (stereoscopic projection, 3D projection), whereby a spatial impression of the 3D image results for the observer because of the stereoscopic effect. Different technologies are known for separating the two partial images, which is also called channel separation.
In polarization filter technology, channel separation is achieved using polarized light. For example, polarizing filter films which are each offset by 90° are located in front of the lenses of a projector. Two projectors are also used for this purpose in cinemas. An observer observes the display through polarization spectacles, which have polarizing filters for separating the partial images superimposed on one another. The polarizing filters of the polarization spectacles are adapted to the polarizing filter films on the lenses of the projector or projectors. A metallically-coated projection screen is required to maintain the polarization status of the light. A normal white projection screen would scatter the light again and the channel separation would be canceled out. Disadvantages are, on the one hand, the light loss due to the filters used and the metallic projection screen and, on the other hand, the fact that if linearly polarized light is used, the head must be held straight during the image observation. If the head is held inclined, the angle of 90°, which is required for the channel separation, between the films in front of the projection lenses and the filters in the filter spectacles changes. A channel separation is thus no longer provided, whereby “ghost images” appear to the observer. This disadvantage can be avoided by using circularly polarized light.
In the Dolby 3D projection method, the partial images of the 3D image are projected with the aid of a broadband light source, wherein the splitting of the 3D image content into two partial images is performed via the splitting of the emitted light spectrum or wavelength spectrum into two spectrally independent color spaces. For this purpose, for example, a color filter is moved frame-by-frame from a first position to a second position. The first position spans a different color space in comparison to the second position. The central wavelengths of the two color spaces do not overlap. For example, a green, red, and/or blue partial image composed of lower (color space A) and higher (color space B) wavelengths is projected alternately, for example, at a frequency of 144 Hz. Alternatively, two projectors, which are equipped with filters which generate the two spectrally independent color spaces, can be used in simultaneous operation. The separation of the image channels and the partial images at the human eye of the observer occurs via filter spectacles having color filters and/or interference filters.
U.S. Pat. No. 6,283,597 B1 discloses a 3D projector, which has two RGB projectors. The two RGB projectors display different images of a 3D image using two different color spaces on a projection surface. Each of the two RGB projectors has multiple optical elements for beam guiding and beam bundling, for example, lenses, prisms, and/or mirrors.
DE 10 2008 063 634 A1 discloses a projector for displaying 2D images, in which the 2D images are projected with the aid of a rapidly moving laser beam spot by spot, line by line so rapidly onto a projection surface that an observer sees the 2D images or films consisting of the 2D images on the projection surface. The projector is also referred to as a flying spot projector.